Semi-interpenetrating polymer network proton exchange membranes with narrow and well-connected hydrophilic channels

► Proton exchange membranes for the direct methanol fuel cells (DMFCs). ► A semi-interpenetrating polymer network (SIPN) based on poly(phenylene oxide). ► Use of cross-linker structure to modify membrane morphology and properties. ► Narrow and well-connected hydrophilic channels are useful for DMFC applications. ► Demonstration of membranes which surpassed Nafion® 117 in single cell tests.